Vision is a very precious possession. The quality of our vision is such that what we see we consider to be reality, in contrast to any other image that mankind is able to produce. It is very difficult to imagine that what we see is actually just an image projected in our brain.
Optometry is an important guardian of the quality of that image in our brain. The present state of optometry is dramatically presented in The Guardian's May 10, 2018 article, “The spectacular power of Big Lens”. It calls out “the accelerating degradation of our eyes” and states, “Vision campaigners forecast that the myopia epidemic will put enormous strain on health systems across the developing world, which are already unable to equip their populations with a medical device that has been around since the Middle Ages.” This crisis calls for a reassessment of what optometry can do for us.
The thermometer is a home use device that measures temperature, providing us with the ability to make important decisions for our well-being. Blood pressure monitors and many other devices provide the same benefit. Unfortunately, an optometer for home use to measure ametropia, that is the presence of refractive errors of the eye, is not available, although it clearly is very much needed.
Optometry is concerned with the measurement of the refractive errors of the eye, such as being out of focus and astigmatism. Optometry is practiced by optometrists and ophthalmologists; the latter profession includes the ability to perform eye surgery. To obtain an assessment of the state of personal ametropia, a visit to an optometrist is presently the only option. It is a significant inconvenience and expense, as compared to other measurements of important bodily data. Considering the present occurrence of ametropia, it is very desirable to be able to make an assessment ourselves, as is done with so many other health conditions.
Optometry is executed objectively and subjectively. The objective method is performed by an optometer called an autorefractor in which the image assessment is based on electronic processing. A test arrangement produces a suitable image on the retina for the measurement of the refractive errors of the eye. The reflection of this image on the retina is made accessible via a beam splitter for processing. The optometer does this work without assistance from the optometrist or the patient and is commonly called an autorefractor. An arrangement is shown in FIG. 1.
The main problem with the objective approach is that the quality of the retina as a reflective projection screen is exceedingly poor. This is to be expected because it is a transmission screen, not a reflective projection screen. The unsuitability of the retina as a reflective projection screen is thus a major and unavoidable limitation of the objective measurement of refractive errors. As the objective measurement may therefore lack accuracy or reliability, it is followed up by a subjective method of measuring the refractive errors.